From 8c8f2bc86eee11c466dc841594e6da518efc45dc Mon Sep 17 00:00:00 2001
From: Project_HSI <57279339+ProjectHSI@users.noreply.github.com>
Date: Tue, 3 Feb 2026 07:42:06 +1000
Subject: [PATCH 1/2] Changed transparent window test

This adds more alpha colours to hopefully diagnose problems with software transparency a bit better.

Theoretically, the squares should be less visible the less alpha down, but with SDL_BLENDMODE_NONE, this is not the case, we need to use SDL_BLENDMODE_BLEND instead.
---
 test/testsoftwaretransparent.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/test/testsoftwaretransparent.c b/test/testsoftwaretransparent.c
index 2ef5598dd3..702bf29462 100644
--- a/test/testsoftwaretransparent.c
+++ b/test/testsoftwaretransparent.c
@@ -27,19 +27,21 @@ static void draw(SDL_Renderer *renderer)
     SDL_RenderClear(renderer);
 
     if (w >= 3 * SQUARE_SIZE && h >= 3 * SQUARE_SIZE) {
-        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
-
         rect.x = 0.0f;
         rect.y = 0.0f;
+        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
         SDL_RenderFillRect(renderer, &rect);
 
         rect.y = h - SQUARE_SIZE;
+        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 170);
         SDL_RenderFillRect(renderer, &rect);
 
         rect.x = w - SQUARE_SIZE;
+        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 85);
         SDL_RenderFillRect(renderer, &rect);
 
         rect.y = 0.0f;
+        SDL_SetRenderDrawColor(renderer, 255, 0, 0, 0);
         SDL_RenderFillRect(renderer, &rect);
     }
 
@@ -82,7 +84,8 @@ int main(int argc, char *argv[])
     }
 
     /* Make sure we're setting the alpha channel while drawing */
-    SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_NONE);
+    /* But also make sure we're setting it to premultiplied alpha and not straight alpha. */
+    SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND);
 
     /* We're ready to go! */
     while (!done) {

From 3ad0e24a077f3e043681ab1e8a4e18e8d5c1db5e Mon Sep 17 00:00:00 2001
From: Project_HSI <57279339+ProjectHSI@users.noreply.github.com>
Date: Wed, 4 Feb 2026 07:14:30 +1000
Subject: [PATCH 2/2] Implement toggle for alpha blending mode

---
 test/testsoftwaretransparent.c | 30 ++++++++++++++++++++++++------
 1 file changed, 24 insertions(+), 6 deletions(-)

diff --git a/test/testsoftwaretransparent.c b/test/testsoftwaretransparent.c
index 702bf29462..f27c4c585c 100644
--- a/test/testsoftwaretransparent.c
+++ b/test/testsoftwaretransparent.c
@@ -15,6 +15,8 @@
 
 #define SQUARE_SIZE 100.0f
 
+static bool premult = false;
+
 /* Draw opaque red squares at the four corners of the form, and draw a red square with an alpha value of 180 in the center of the form */
 static void draw(SDL_Renderer *renderer)
 {
@@ -26,6 +28,8 @@ static void draw(SDL_Renderer *renderer)
     SDL_SetRenderDrawColor(renderer, 0, 0, 0, 0);
     SDL_RenderClear(renderer);
 
+    SDL_SetRenderDrawBlendMode(renderer, premult ? SDL_BLENDMODE_BLEND : SDL_BLENDMODE_NONE);
+
     if (w >= 3 * SQUARE_SIZE && h >= 3 * SQUARE_SIZE) {
         rect.x = 0.0f;
         rect.y = 0.0f;
@@ -49,6 +53,9 @@ static void draw(SDL_Renderer *renderer)
     rect.x = (w - SQUARE_SIZE) / 2;
     rect.y = (h - SQUARE_SIZE) / 2;
     SDL_RenderFillRect(renderer, &rect);
+
+    SDL_SetRenderDrawColor(renderer, 0, 255, 255, 255);
+    SDL_RenderDebugText(renderer, 0, 0, premult ? "Premult'd" : "Straight");
 }
 
 int main(int argc, char *argv[])
@@ -61,7 +68,7 @@ int main(int argc, char *argv[])
 
     int return_code = 1;
 
-    state = SDLTest_CommonCreateState(argv, 0);
+    state = SDLTest_CommonCreateState(argv, SDL_INIT_VIDEO);
     if (!state) {
         return 1;
     }
@@ -83,12 +90,10 @@ int main(int argc, char *argv[])
         goto quit;
     }
 
-    /* Make sure we're setting the alpha channel while drawing */
-    /* But also make sure we're setting it to premultiplied alpha and not straight alpha. */
-    SDL_SetRenderDrawBlendMode(renderer, SDL_BLENDMODE_BLEND);
-
     /* We're ready to go! */
     while (!done) {
+        bool renderNeeded = false;
+
         while (SDL_PollEvent(&event)) {
             switch (event.type) {
             case SDL_EVENT_KEY_DOWN:
@@ -98,7 +103,15 @@ int main(int argc, char *argv[])
                 break;
             case SDL_EVENT_WINDOW_EXPOSED:
                 /* The software renderer is persistent, so only redraw as-needed */
-                draw(renderer);
+                renderNeeded = true;
+                break;
+            case SDL_EVENT_MOUSE_BUTTON_DOWN:
+                if (event.button.button == 1) {
+                    // switch between premultiplied alpha and straight alpha
+                    premult = !premult;
+
+                    renderNeeded = true;
+                }
                 break;
             case SDL_EVENT_QUIT:
                 done = true;
@@ -108,6 +121,9 @@ int main(int argc, char *argv[])
             }
         }
 
+        if (renderNeeded)
+            draw(renderer);
+
         /* Show everything on the screen and wait a bit */
         SDL_RenderPresent(renderer);
         SDL_Delay(100);
@@ -123,3 +139,5 @@ quit:
     SDLTest_CommonDestroyState(state);
     return return_code;
 }
+
+